Recently, microstructure devices, for example, various sensors using MEMS (Micro Electro Mechanical Systems), have been used in various fields including automobile and medical technology. As electronic devices have been made small and light and have high-level functions, the development of MEMS has also been promoted. Since MEMS are micro-fabricated systems, there is a demand for an appropriate method of inspecting the MEMS.
Examples of a method of measuring mechanical characteristics, such as an attenuation factor (ζ), a Q value, a natural frequency (f0), and a loss factor (τ), of a microstructure include a method of obtaining a decay curve by using an impulse hammer, and a method of obtaining a resonance frequency by intentionally scanning an excitation frequency of a structure and thus obtaining an attenuation factor from a FWHM (Full Width at Half Maximum) of a resonance curve.
Patent Document 1 or Patent Document 2 discloses a method of causing a test sound wave to be output from a speaker to a moving portion of a sensor to move the moving portion, and thus inspecting electrical characteristics of a microstructure by using a probe. Patent Document 3 discloses a method of detecting a change in the resistance value of an acceleration sensor formed on a wafer by blowing air and thus determining the property of the acceleration sensor.
Also, Patent Document 4 discloses a method of outputting an ultrasonic wave to a moving portion to induce slow dynamics on an object, and measuring a physical change. Also, Patent Document 5 discloses a method of intermittently generating a longitudinal wave by using a sound wave generating element of thermal excitation type, and thus detecting a distance to an object and an orientation where the object is located. Also, Patent Document 6 discloses a method of causing a PZT (lead zirconate titanate) ultrasonic wave transforming device to directly contact a microstructure, and thus measuring a dynamic response.    (Patent Document 1) Japanese Laid-Open Patent Publication No. 2007-108157    (Patent Document 2) International Publication No. 2006/093232 Pamphlet    (Patent Document 3) Japanese Laid-Open Patent Publication No. Hei 5-34371    (Patent Document 4) Japanese Laid-Open Patent Publication No. 2004-523768    (Patent Document 5) Japanese Laid-Open Patent Publication No. 2006-220637    (Patent Document 6) Specification of U.S. Pat. No. 6,595,058